A strut-type suspension used for a front wheel of an automobile has structure in which a strut assembly is combined with a coil spring. This strut assembly comprises an external cylinder, which is integrated with a piston rod, and a hydraulic shock absorber housed in the external cylinder. When the steering is operated, the strut assembly is rotated together with the coil spring. Accordingly, for allowing smooth rotation of the strut assembly, a rolling bearing or a sliding bearing is placed as a thrust bearing between an upper support which is a mounting mechanism for mounting the strut assembly onto the automobile body and an upper spring seat which is a spring seat positioned at the upper end of the coil spring.
For example, the Patent Literature 1 discloses a sliding bearing made of synthetic resin as a thrust bearing for a strut-type suspension. This sliding bearing comprises: an upper case, which is attached to the side of an upper support; a lower case, which is attached to the side of an upper spring seat and rotatably combined with the upper case; and a center plate, which is placed in an annular space formed by combination of the upper case and the lower case and functions as a bearing body realizing smooth rotation between the upper case and the lower case. Here, the annular space formed by the combination of the upper case and the lower case is filled with lubricating grease. Further, in a bearing surface of the center plate, are formed, as lubricating grease reservoirs, an annular groove located on the radially inner side of the bearing surface and a plurality of grooves extending radially outward from the annular groove to connect with the side surface.